The technical scope of the present invention is that of devices to drive a load with reduced or no backlash between the motor and the load.
When a load is driven in movement, and notably in rotation, the backlash between said load and the drive motor must be reduced to a minimum so as to obtain the precise positioning of the load with respect to a given reference. This problem is of extreme importance within the scope of the laying of a weapon mounted in the turret of an armed vehicle.
Various principles to eliminate any backlash are known and used in various branches of the technique.
By way of illustration, patent FR-2221981 proposes two independent and slightly opposing chains to eliminate the problems of backlash, but using two motors. This is the main drawback to this device.
Patent FR-2538136 proposes to release the servo-driven chain from the elasticity of the transmission so that the motorisation is comparable to that of a torque motor connected directly to the load. In the proposed system, the motorisation is constituted by a motor connected to the load by two reduction gears whose elasticity is employed to eliminate the backlash in a transmission by reduced prestressing. This reduced prestressing is enough to absorb the different homokinetic type errors that may appear between motor and load. This system is perfectly well adapted when the ratio between the elasticity of the reduction gears and the maximal homokinetism error is high.
However, when the harmonisation errors exceed around 10% of the clearance between the motor and the load required to transmit the maximum motorisation torque, the principle of approximately fixed prestressed load is used to avoid the arcing of two chains set in parallel, locally or globally over the full kinematics. The invention aims to supply a device having this property.